This invention relates to a method for the production of a fibrous material containing curled fibers and comprising the steps of passing a raw material sheet of cellulosic fibers into a defibrator and drawing a stream of gas containing the so-formed fibers suspended out of the defibrator. The stream of gas is intended to be passed through a forming wire to form a fibrous sheet.
The fibers to be used in the present invention comprise cellulosic fibers, wood fibers, mixtures with synthetic fibers including bicomponent fibers and synthetic fibers. The synthetic fibers may, e.g., be of polypropylene or polyethylene. Also glass fibers, rock wool fibers, and pretreated fibers may be used.
When making a fibrous sheet material containing curled fibers it is customary to add curled fibers to the cellulosic fibers. Curled fibers containing a thermoplastic resin are advantageous due to the softness and the pliability of such curled fibers and the ability to use the thermoplastic material as a binder instead of using latex binders. However, curled bi-component fibers are very expensive in comparison with ordinary cellulosic fibers. The curled fibers are also expensive in relation to rectilinear bi-component fibers. Thus the cost of curled bi-component fibers is approximately double the cost of rectilinear bi-component fibers.
When rectilinear synthetic resin-containing fibers are used, a better bonding is obtained instead of the use of a latex binding. However, there is a risk that the rectilinear synthetic fibers extend outside the product. Thus the product will appear with a poor hand and feel. Thus, it will not have a good wearing comfort as it is rough and unpleasant for the user. When curled synthetic fibers are used instead, the synthetic fibers will not extend outside the product. This is due to the fact that the curled synthetic fibers are soft and pliable. Thus, the fibers will remain inside a web formed even if the web is folded.
It is the object of the present invention to provide a method making it possible to use rectilinear bi-component fibers in the manufacture, however, having the effect of the curled bi-component fibers in the final product.
It is a further object of the invention to provide a method in which the curling of the bi-component fibers is effected simultaneously with the defibration of the raw material sheet of cellulosic fibers.